I'll play the role of Canon Guy. Nikon Guy will be here shortly. If we're lucky, Pentax Guy might make a brief cameo.
You can pick up a Rebel XS for around $500. A lot of stores will also throw in a bag and an 80-200 lens for not much more. The XS has more autofocus points than comparable Nikons. Canons generally shoots better JPEGs than Nikons, if you're into that sort of thing. They shoot a little faster in continuous mode. They're a little lighter. And the big selling point, to me - Canons have the autofocus motors in-body instead of in the lens, which makes lenses cheaper and faster, and allows you to use pretty much any Canon lens made in the past 20 years. Nikons are a lot pickier about the lenses they'll take.
The one feature that the entry-level Nikons have that I envy is spot metering. Higher-end Canons have it, but for some reason the cheaper ones don't. It's not a game changer by any means, and if you don't know what spot metering is then you're not going to miss it. It's just a nice feature to have.
Well, as a "Nikon guy" im going to have to go ahead and disagree with you on basically everything. Lol, no, but the Rebel XS has 7 points of AF to the D3000's 11, both have 3 frames per second continuous shooting, and the Rebel XS is only .02 ounces lighter than the D3000.
I'll concede that the built in motor is an attractive feature that makes Canon's interesting. I have a few lenses from my dad's 35mm that I would have liked to use, but alas. In addition, there is a Nikon to Canon adapter if you have Nikon lenses. (Edit-I think I should make it clear that since the AF motor is built into Nikkor lenses, older lenses (F Mount only) that are manual focus will not have autofocus.)
I'm also Nikon Guy. Both brands are good, but because you are going to be heavily investing into one lens or the other, it tends to develop a lot of brand loyalty. For instance I can't even really shoot Canon without a substantial investment cause all my glass is Nikon. both are totally legitimate, and have some areas that one excels in versus the other.
There's a few really good entry level Nikon bodies, and you can even save on the body by buying/using your own lenses and skipping the kit lens. If you're just getting into DSLRs, keeping the kit lens may be some good introductory practice with a 'jack of all trade' type lens.
the D60 is a very reliable starting body that isn't too expensive, as is the D3000. I started with the D60 myself, but I have friends that really liked the D3000. It's always a better idea to save on body and get a nicer lens than the other way around. The lens is always gonna matter more. I've never had any complaints with my old D60 though. All can come in under your budget as well.
SInce you don't have very specific shooting plans, one of these and some general purpose lens will be a great idea. A 50mm/f1.8 is really really cheap (<$100) and takes awesome shots, but you'll have to manually focus on most lower end nikon bodies. Good practice though. Sigma makes some nice cheaper lenses for either canon or nikon bodies as well. Their 17-70mm macro lens has been a great all-purpose walk around lens for me. Really cheap too (maybe $200-300?)